Method of producing castings



Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE mesne assignments,

to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application July 26, 1933,

' Serial No. 682,275

4 Claims.

The present invention is based on the discovery that the hardening effect of carbide forming elements is decreased, and the strength, ductility, and machinability of the casting are improved, if a substantial amount of a graphitizing agent,

any given casting composition without decreasing or destroying machinability.

All cast irons containing more than about 1% carbon may be benefited by the use of the invention. In general, the final composition of the 5 casting should be substantially 1% to 4% carbon, 1% to 4% graphitizing agents, 0.15% to 1% manganese, up to about 0.5% sulfur, 0.05% to 0.3% phosphorus, 0.1% to 35% carbide forming elements, remainder iron. The greatest use of the invention may be in producing castings containing 0.1% to 2% chromium as the carbide forming element; .but the improvement in properties is found to be marked in castings containing up to 35% and more chromium or other carbide forming element.

The table given below is illustrative of the improvement in the properties of cast iron attainable according to the invention:

Analysis of casting Transverse tests Tensile Hardness Casting number Ladle addition strength, Briuell 950; %Bi 3 53 Defl. m. Pmmds Nil 2. 52 3,050 0.093 31,400 170 1.01 2. 3,100 0.000 41,050 310 1.00 2. 42 5,025 0.153 00,550 200 14.04 2. 52 3,000 0,01 14.59 an 4,000 0.085

for example, silicon, nickel, aluminum, or zir- Ingeneral, the invention provides castings havconium, is added to the molten iron shortly before ing a, transverse test strength greater than about the melt is cast rather than during the initial 4500 pounds, as compared to 3000-4000 pounds melting period. The graphitizing agent is prefin iron castings previously known. erably added in the ladle. The analyses of castings 1, 2, and 3, respec- When a graphitizing element is added in th tively, were substantially identical with the exabove described manner shortly before pouring, ceptionof the chromium content of casting num-' a marked increase in strength, ductility, and maher 1. Likewise, the analyses of castings 4 and 5 chinability results, as compared to a casting havwere substantially identical. The silicon in cast- 40 ing the same composition but treated with the ings numbers 1, 2 and 4 was added in the furnace graphitizing agent, at a time other than shortly in the usual manner; while part of the silicon before pouring. The treatment also results in a in castings numbers 3 and 5 was added in the marked refinement of the structure of the castladle. Casting number 3 was materially stronger, ing, and serves to break up or to inhibit the more ductile, and more easily machinable than formation of large crystallites of carbides, which casting number 2, and stronger, harder, and more doubtless contributes to the improved machinawear resistant than casting number 1. Similarly, bility and strength of the castings. The best. casting number 5 was materially stronger and results are obtained when the amount of silicon more easily machinable than casting number 4, and other grap t agents present during the The graphitizing agent may be added as a meltin p r d s relatively low so t a a large metal or a ferroalloy. The carbide forming agent proportion of the total final silicon may be dded may be added in the furnace or in the ladle, as immediate y before casting a metal, ferroalloy, or compound. If chromium The invention thus affords a means of increasand silicon are both' to be added in the ladle, the ing the content of carbide forming element in addition may, conveniently be made as a siliconchromium alloy, or as a ferrochromium-silicon alloy, or as a low melting copper, chromium, silicon alloy.

I claim:

1. Method of producing a ferrous alloy casting having substantially the composition: 0.1% to chromium, 1% to 4% silicon, 1% to 4% carbon, 0.15% to 1% manganese, up to about 0.5% sulfur, up to about 0.3% phosphorus, the remainder iron, and characterized by improved machinability, ductility, and strength, which comprises forming a melt the silicon content of which is materially less than is desired in the casting, adding silicon, and casting the melt substantially immediately after the addition of silicon.

2. Method of producing a ferrous alloy casting having substantially the composition: 0.1% to 15% chromium, 1% to 4% silicon, 1% to 4% carbon, 0.15% to 1% manganese, up to about 0.5% sulfur, up to about 0.3% phosphorus, the remainder iron, and characterized by improved machinability, ductility, and strength, which comprises forming a melt the silicon content of which is materially less than is desired in the casting, add-- ing silicon, and casting the melt substantially immediately after the addition of silicon.

3. Method of producing a ferrous alloy casting having substantially the composition: 0.1% to 2% chromium, 1% to 4% silicon, 1% to 4% carbon, 0.15% to 1% manganese, upto about 0.5% sulfur, up to about 0.3% phosphorus, the remainder iron, and characterized by improved machinability, ductility, and strength, which comprises forming a melt the silicon content of which is materially less than is desired in the casting, adding silicon, and casting the melt substantially immediately after the addition of silicon.

4. Method of producing an alloyed cast-iron casting containing from 0.1% to 15% chromium which comprises forming a melt of chromiumalloyed iron the silicon content of which is materially less than is desired in the casting, adding silicon, and casting the melt substantially immediately after the addition of silicon, whereby is produced a casting having a structure consisting chiefly of a pearlitic ground mass, small graphite flakes, and small widely dispersed non-dendritic carbide particles distributed substantially uniformly throughout the ground mass the proportion of carbide present being only a minor fraction of that normally present in cast iron of similar composition.

CHARLES 0. BURGESS. 

